1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a fax machine, a printer or the like, and more particularly to a charging device of an image carrier used in such an image forming apparatus.
2. Description of the Related Art
Contact-type charging devices, in which an image carrier is brought into pressure contact with a charging member such as a charging roller, charging brush or the like to which voltage is applied, are known as conventional charging devices of image carriers. Such contact-type charging devices are likely to exhibit problems over time such as contamination, caused by residual toner on the image carrier becoming adhered to the charging member, which preclude uniform charging. A cleaning member such as a pad, roller or the like is therefore provided for cleaning the charging member. However, providing a cleaning member drives costs up. Another problem is contamination of the cleaning member over time, which impairs the function of the cleaning member.
Also known are image forming apparatuses in which an electric field is formed between the image carrier and the charging member such that toner adhered to the surface of the charging member is caused to migrate towards the image carrier. By way of such an electric field, toner adhered to the surface of the charging member is thus cleaned electrostatically by the image carrier (Japanese Unexamined Patent Application Laid-open No. S58-42067 and Japanese Unexamined Utility Model Application Laid-open No. S58-54644).
The above image forming apparatuses where a charging member is cleaned electrostatically are problematic, however, in that toner strongly adhered to the charging member cannot be fully removed.